Seaborn box plot returns a matplotlib axes instance. Unlike pyplot itself, which has a method plt.title(), the corresponding argument for an axes is ax.set_title(). Therefore you need to call

sns.boxplot('Day', 'Count', data= gg).set_title('lalala')

A complete example would be:

import seaborn as sns
import matplotlib.pyplot as plt

tips = sns.load_dataset("tips")
sns.boxplot(x=tips["total_bill"]).set_title("LaLaLa")

plt.show()

Of course you could also use the returned axes instance to make it more readable:

ax = sns.boxplot('Day', 'Count', data= gg)
ax.set_title('lalala')
ax.set_ylabel('lololo')

sns.boxplot() function returns Axes(matplotlib.axes.Axes) object. please refer the documentation you can add title using 'set' method as below:

sns.boxplot('Day', 'Count', data=gg).set(title='lalala')

you can also add other parameters like xlabel, ylabel to the set method.

sns.boxplot('Day', 'Count', data=gg).set(title='lalala', xlabel='its x_label', ylabel='its y_label')

There are some other methods as mentioned in the matplotlib.axes.Axes documentaion to add tile, legend and labels.

Try adding this at the end of your code:

import matplotlib.pyplot as plt

plt.title('add title here')